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Let `veca=hati + 2hatj +hatk, vecb=hati - hatj +hatk and vecc= hati+hatj-hatk` A vector in the plane of `veca and vecb` whose projections on `vecc`` `is` `1//sqrt3` isA. `4 hati - hatj + 4hatk`B. `3hati+hatj - 3hatk`C. `2hati+hat- 2hatk`D. `4hati + hatj -4hatk` |
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Answer» Correct Answer - a A vector in the plane of `veca and vecb` is `vecu=muveca +lambdavecb= (mu +lamda)hati+ (2mu - lamda) hatj + ( mu +lambda)hatk` projection of `vecu` on ` vecc = 1/sqrt3` ` Rightarrow (vecu.vecc)/(|vecc|)= 1/sqrt3` `or vecu.vecc=1` `or |mu + lambda+ 2mu -lamda-mu-lambda|=1` `or |2mu -lamda|=1` `or lamda = 2mu +- 1` `Rightarrow vecu = 2hati +hatj + 2hatk or 4 hati -hatj + 4hatk` j |
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